The good news is that it's now possible. It's been possible for a while actually just that most people didn't know about it!
You can perform these Modifications on your smartphone by simply using an app known as ButtonRemapper apk. :p
What is ButtonRemapper
The app does what the name says. It simply changes what a button does on Android Smartphone and gives it another function as specified by the user.
WHat can one modify/assign with this app?
"Power",
"Home",
"Menu",
"Back",
"Search",
"Volume up",
"Volume down",
"Camera",
"Focus",
"Endcall",
"Call",
"Media Play Pause",
"Media Stop",
"Media Next",
"Media Previous",
"Media Rewind",
"Media Fast Forward",
"Dpad center",
"Dpad up",
"Dpad down",
"Dpad left",
"Dpad right"